The cosmetic compositions intended to coat keratinous fibers, whose purpose in generally makeup and/or care, traditionally comprise coloring material such as mineral pigments, for example. In addition, the cosmetic compositions intended to coat keratinous fibers and which must be resistant to water, steam, humidity, sebum, and tears (mascara formulations, for example) generally comprise a film-forming polymer. The person skilled in the art tries to control the rheological, particle size distribution, stability, and sensory parameters during the implementation, storage, and post-use of the cosmetic compositions and, more specifically, of the compositions for coating keratinous fibers that comprise mineral or organic fillers, notably mineral pigments. For this purpose, they use dispersing additives or dispersing agents.
These dispersing agents are capable of dispersing the mineral pigments, for example metal oxide pigments such as iron oxide, in the compositions that contain them. In fact, a dispersing agent is typically used in order to prevent the flocculation of the particles and the ensuing loss of the desired properties. In practice, a dispersing agent included in a cosmetic formulation comprising metal pigments, leads to a viscosity lower than that of the same cosmetic formulation that does not contain said dispersing agent. The dispersing power of an agent in a formulation is thus measured by determining the viscosity. In addition, dispersing agents make it possible to stabilize the particle size distribution and texture parameters of the compositions. They make it possible to homogenize said compositions.
There are four broad categories of dispersing agents in cosmetic compositions: oils, surfactants, natural dispersants, and polymeric-type dispersants.
Additives of the cosmetic oils type, for example esters, such as the poly(hydroxystearic) acids, and some surfactants are commercially available for dispersing the iron oxides in cosmetic formulations for keratinous material. Nevertheless, these additives have the drawback of negatively impacting the sensory aspect of the compositions that include them; their use in these compositions is, therefore, limited.
Among the dispersants of natural or biosourced origin, one can mention the use of lignosulphonates and carbohydrates of the inulin type (Abstract of Paper, 244th ACS National Meeting & Exposition, Philadelphia, Aug. 19-23, 2012 Washington D.C.) and of acyl-poly(aminoacid), of poly-glutamate (US 20120076840 and JP 2012001503), and of poly(aspartic) acids. These natural dispersants have the drawback that they need to be purified in order to attain the molecular weight desired for optimum effectiveness as dispersing agents in cosmetic compositions.
A number of documents in the prior art discuss the dispersion of mineral filler pigments with polymeric additives.
One can cite, among them, J. Cosmet. Sci., 50, 105-109, 1999, which concerns, in a general way, the water-based nail polish additives and which describes, notably, the implementation of water-soluble polymers as thickeners, stabilizers, and pigment dispersants. The homopolymers of ethylene oxide, of acrylic acid, of methacrylic acid, of polyvinyl alcohol, and of various cellulosic materials are examples of these additives.
One can also cite the article Tenside Surf. Det., 36, 1999, which discusses a technical area different than that of this invention. This document describes the impact of polymeric and non-polymeric materials on the dispersion of iron oxide particles in the water used in industrial processes (for example in heat exchangers and distillation systems). The following polymers are specifically mentioned: polymers of acrylic acid, methacrylic acid, maleic acid, acrylamide, 2-acrylamido-2-methylpropane sulphonic acid, and copolymers of acrylic acid.
Patent WO 2009073384 describes the use of acrylic organosilylated copolymers. These commercially available copolymers have a non-negligible impact on the sensory and organoleptic properties of cosmetic formulations.
In addition, incompatibility problems are encountered in the cosmetic compositions which contain coloring mineral pigments of the metal oxide type, such as iron oxides, and which also comprise film-forming polymers and dispersing agents of the polymeric type. The simultaneous presence of two types of polymers within the cosmetic composition can, in some cases, lead to instability problems, such as dephasing or phase separation, bleeding, release, and deposition or sedimentation. This incompatibility becomes more important as the concentrations of pigments and/or film-forming polymers (also called agent or film-forming additive) are increased in said cosmetic compositions.